Processes for incorporating ground tire rubber into bituminous material to make asphalt cement systems suitable for paving, roofing and other uses have hitherto been unduly complex and thus costly in use. Known processes use additional constituents of the composition and additional process steps in an attempt to provide a homogenous system. Such attempts have not been successful.
Duong et al., U.S. Pat. No. 5,270,361, is directed to a process for making an asphalt composition which includes synthetic or natural rubber which may be in particles of up to one-half inch in thickness. Elemental selenium or an organo-selenium compound is added into the mixture to act as a substitute for the sulfur which is removed during the devulcanization process. The selenium or organo-selenium compound acts as a cross-linking agent. The composition is treated with pressurized air in a dehydrogenation reaction. In the dehydrogenation vessel, the dispersing device includes a pair of discs turning at 3600 rpm which promotes homogenization and acceleration of the dehydrogenation reaction. Elemental selenium or an organo-selenium compound is added into the homogenized composition and mixed in a static mixer. The asphalt composition is then recovered and stored in a container at about 150.degree. to 175.degree. C.
Wilkes, U.S. Pat. No. 4,609,696, describes a rubberized asphalt composition which is made by combining asphalt with a hydrocarbon oil to provide a homogenized asphalt-oil mixture or solution, combining the mixture with particulate rubber to provide a homogenous gel and emulsifying the gel by passing the asphalt-rubber-oil gel, with water, through a colloid mill.
Oliver, U.S. Pat. No. 4,430,464, describes a pavement binder composition in which rubber particles are digested in a bituminous material. McDonald, U.S. Pat. Nos. 4,069,182 and 3,891,585, describe an elastomeric pavement repair composition and a method for making the composition. Winters et al., U.S. Pat. No. 3,919,148, also describes an elastomeric paving material.
Pagen et al., U.S. Pat. No. 4,588,634 describes a roofing material using bitumen and ground tire rubber together with mineral stabilizer and an elastomeric polymer composition.